#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main() 
{
    float r1 = 0, r2 = 0;
    scanf("%f %f", &r1, &r2);
    float R = 1 / (1.0 / r1 + 1.0 / r2);
    printf("%f", R);
    return 0;
}